The subject invention relates to centralizing devices for locating a casing or pipe string concentrically within a well bore or another casing and particularly is directed to a non-weld centralizer which can be packaged in originally disassembled form for space efficient shipping and easily and conveniently finally assembled in the shop or place of business of the purchaser or actually on the job site.
Centralizer devices generally comprise upper and lower collar members having a plurality of outwardly bowed spring members attached at the upper and lower ends thereof in various manners or ways to the collars. Such collars conventionally are constructed of two or more arcuate sections with various means for joining the arcuate section together after being placed around a pipe or casing. The spring members may be welded to the collar sections or mechanically attached thereto by various means and devices.
In use, centralizers are ordinarily supported on a pipe or casing at vertically spaced locations along its length. The outwardly bowed spring members yieldably engage the well bore or another casing circumferential thereto at spaced locations therealong. The well pipe may be a casing disposed within an open well bore or within another casing in the well bore which, when centered, permits a uniform column of cement to be pumped into the annular space between it and the well bore.
When mounted on a pipe or casing section, centralizers are supported for limited endwise movement by one or more stop collars, the latter fixedly clamped or attached about the pipe or casing. A pair of such collars may be attached to the casing above and below the centralizer collars or a single stop collar may be clamped or otherwise attached to the casing intermediate the centralizer collar sleeve ends. Or both. In either case, the stop collars or stop members are so located with respect to the centralizer collars that the latter are freed to move toward and away from one another as the bowed springs expand and contract. This permits the centralizers to function in well bores of somewhat different diameters.
A major factor in the design of many centralizers is the manner in which the bowed spring members are connected or connectible to the end collars of the centralizer. Such connection governs the manner in which the centralizers may be originally assembled at a purchaser's shop, field installation, on the job site, etc. or disassembled for shipping and reassembled away from the point of manufacture. Clearly, a fully assembled centralizer occupies a relatively great volume compared to the volume required for its component elements nested or packed in sets for shipping. In order to minimize the shipping costs of centralizers to distant locations, non-weld centralizers or centralizers that are easily entirely or partially assembleable by the purchaser or in the field have been developed. Many prior such designs have been provided, some of which are noted in the Prior Art section given herebelow. A basic factor with respect to any centralizer construction, however, is that it must be not only structurally sound when assembled, it must also be sufficiently strong that it will function in the well bore environment and not be easily damaged by the rough treatment encountered in well bore use.
Another important factor which is often not sufficiently considered in other centralizer designs or not present or allowed for in other centralizer designs is that the crew at the job site or assembly point may be under job site conditions which preclude sophisticated handling of complexly shaped pieces. Yet further, job site or assembly point personnel may be generally relatively unsophisticated with respect to complex apparatus assembly. Thus, in order to be effective, and useful in its job, a centralizer assembleable away from the point of manufacture or at the job site should be of extremely simple construction and assemblable in a manner that does not heavily tax either the facilities or skills of the job site personnel.